Answer:
IQR = 4
Explanation:
the IQR is the difference between the upper quartile (Q₃ ) and the lower quartile (Q₁ )
the first step is to find the median (Q₂ )
the median is the middle value of the data set , arranged in ascending order ( smallest to largest )
given the set of numbers in ascending order.
20 , 21 , 22 , 23 , 24 , 25 , 25 , 25 , 26 , 27 , 28
↑ middle value
median = 25
the upper quartile Q₃ is the middle value of the numbers on the right of the median.
25 , 25 , 26 , 27 , 28
↑ middle value
upper quartile Q₃ = 26
the lower quartile Q₁ is the middle value of the numbers to the left of the median
20 , 21 , 22 , 23 , 24
↑ middle value
lower quartile Q₁ = 22
the interquartile range is then
IQR = Q₃ - Q₁ = 26 - 22 = 4